You can move the p1 joystick left then right to simulate the "OK". So there is no need to open your cabinet and grab the keyboard.
There should never be a need anyway since you should be using a wireless keyboard.

The only thing you can disable through the ini is the game info screen. Game warnings as well as the disclaimer can no longer be turned off or on by the ini file. That code was removed.
You could create .cfg files for every game in your system. If the code sees this file it thinks you have played the game before and won't show the disclaimer. However, this will NOT stop it from presenting the warnings screen (this screen says that sounds isn't accurate, video isn't accurate, cocktail flipping, etc).
The only way to remove those (and the easiest way in my opinion) is to just change the code and recompile your own version of mame.